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Results for “physiological characteristics”

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At least 181 records · Page 10Linked to original sources
PubMed2000

Correlations between morphological, molecular biological, and physiological characteristics in clinical and nonclinical isolates of Acanthamoeba spp.

Eleven Acanthamoeba isolates, obtained from Acanthamoeba keratitis patients, from contact lens cases of non-Acanthamoeba keratitis patients, from asymptomatic individuals, from necrotic tissue, and from tap water and two reference strains were investigated by morphological, molecular biological, and physiological means in order to discriminate clinically relevant and nonrelevant isolates. All clinically relevant isolates showed Acanthamoeba sp. group II morphology. 18S ribosomal DNA sequencing revealed sequence type T4 to be the most prevalent group among the isolates and also the group recruiting most of the pathogenic strains. Interestingly, within T4 the strains of no clinical relevance clustered together. Moreover, physiological properties appeared to be highly consistent with initial pathogenicity and with sequence clustering. Altogether, the results of our study indicate a correlation between the phylogenetic relationship and pathogenicity.

Acanthamoeba↗
PubMed2003

Use of proteomics and physiological characteristics to elucidate ecotoxic effects of methyl tert-butyl ether in Pseudomonas putida KT2440.

We monitored rates of growth, ATP-synthesis, respiration, and death to assess the sensitivity of the model organism Pseudomonas putida KT2440 to methyl tert-butyl ether (MTBE), and its degree of toxicity. The physiological data obtained suggested that the energy conservation system was the most sensitive site. However, with the help of proteomic analysis we obtained further information and deeper insight into the molecular mechanisms involved. This analysis indicated that sensitivity involves oxidative stress since alkylhydroperoxide reductase C (AhpC) and two superoxide dismutases (SodM, SodF) were amplified in the presence of MTBE. Thus, proteomics has major advantages in ecotoxicological investigations where the aims include elucidation of the molecular mechanisms as well as characterization of the ecostress and the potency of the stressor(s).

Adenosine Triphosphate↗
PubMed2000

Vertebrate Secondary Sexual Characteristics-Physiological Mechanisms and Evolutionary Patterns.

As most commonly presented, the organization-activation theory of sexual differentiation emphasizes the importance of the relative age of the organism for understanding steroid hormone effects. However, considering the actual physiological mechanisms of tissue enlargement (hyperplasia/hypertrophy) provides an additional perspective for interpreting patterns of evolutionary change in sexual dimorphism. Using that focus, it is possible to suggest mechanistic explanations for patterns of allometry and the size of some secondary sexual characteristics produced by "runaway" selection. It can also lead to the formulation of testable hypotheses regarding the type of sexually dimorphic characters that might evolve through "good genes" models; the relationship between intrasexual competition, polygyny, and the development and size of male weapons; and the control and type of secondary sexual characteristics that will be present in males with associated and disassociated reproductive patterns.

Journal Article↗
PubMedDate not supplied

[Recent findings regarding physiological characteristics and effects of renal dopamine].

During the past decade, it has become evident that dopamine acts not only as a classical neurotransmitter in the central and peripheral nervous system but also as an autocrine, paracrine and/or endocrine substance in peripheral, non-neuronal tissues. This work is aimed to review some of the recent aspects related to the physiological features and effects of renal origin dopamine. Renal dopamine is synthesized in the proximal tubule epithelial cells. Newly formed dopamine leaves the cellular compartment by crossing the apical cell border and the basolateral membrane side. Dopamine exerts its intrarenal action via specific cell surface receptors, differentially expressed along the nephron and other structural components of renal tissue. These receptors have been classified into five types. D1 and D5 receptors are linked to stimulation, while D2, D3 and D4 receptors are linked to inhibition of adenylyl cyclase. Renal dopamine affects electrolyte and fluid balance by regulation of renal excretion of electrolytes and water through actions on renal hemodynamics and tubular, epithelial transport. The importance of intrarenally produced dopamine as a natriuretic hormone is reflected by its capacity to inhibit the majority of sodium transporters (Na+K+ATPase, Na+/H+-exchanger) in the entire nephron. Numerous clinical and animal, experimental observations suggest that dopamine coordinates the effects of antinatriuretic and natriuretic factors and indicate that the intact renal dopamine system is of major importance for maintenence of sodium homeostasis and systemic blood pressure. Sodium retention leads to an increase in renal dopamine tonus. This function is, due to deficient renal dopamine production and/or a D1 receptor G-protein coupling defect, lost in human essential hypertension and in some animal models of genetic hypertension. A better knowledge of molecular bases of these changes may contribute to the development of specific diagnostic and therapeutic approaches in essential as well as secondary forms of hypertension.

Animals↗
PubMed1992

[Genetic analysis of various behavioral and physiologic characteristics in hybrids between hypertensive and normotensive rats. Analysis of reciprocal differences].

As a result of reciprocal crosses between the SHR rats (spontaneously hypertensive strain) and WKY rats (normotensive strain), two types each of the F1 and F2 hybrids and 4 types of backcrosses were obtained. Analysis of reciprocal differences carries out in these generations for a number of behavioral and physiological traits demonstrated linkage of an hereditary factor affecting expression of potassium appetite with the Y-chromosome. The maternal effect contrary to the action of chromosomal hereditary factors was established for locomotor activity in the peripheral zone of open field. This maternal effect was manifested in the F1 and F2 generations, but not in backcrosses.

Animals↗
PubMed1991

Physiological characteristics of elite female basketball players.

Successful performance in international basketball competition requires an appreciation of the physical demands of the sport and the capacities of the team to respond to those demands. Optimal performance now requires a combination of technical and tactical abilities as well as a high degree of physical fitness. The objectives of this study were to assess physiological components considered important to game performance in players selected to the national team roster in 1988 or 1989, and to use this information to describe the team and positional profiles. Data obtained from maximal treadmill tests, anthropometry, sprints, isokinetic dynamometry, and other tasks reflected those qualities required of elite players. In relation to previously reported data, the athletes were generally taller and heavier and had higher maximal aerobic power than international and college players of 7 to 10 years ago. The data can also be used to identify target standards for current and prospective team members.

Adult↗
PubMed1997

Biochemical and physiological characteristics of HlyA, a pore-forming cytolysin of Vibrio cholerae serogroup O1.

Among the various toxins produced by the bacterial species Vibrio cholerae is HlyA, a cytolytic protein commonly called the E1 Tor hemolysin. HlyA is synthesized and processed in a complex manner involving various processed or degraded forms, that may co-purify and complicate the interpretation of biochemical and physiological experiments. In this study a single form of HlyA was purified by gel filtration and chromatofocusing using fast protein liquid chromatography in the presence of protease inhibitors. A 45-fold purification was obtained, with a final recovery of 17% of pure 60,000 mol. wt HlyA. A significant improvement in specific activity to 8.5 x 10(6) Chinese hamster ovary tissue culture units per mg protein was obtained. Physiological activity studies indicated that cytolysis of erythrocytes (hemolysis) was inhibited by oxygen: storage of HlyA under oil, and experimentation in N2-flushed buffers maintained activity. HlyA-mediated lysis of human erythrocytes was characterized by a significant lag phase, followed by a rapid induction of hemolysis. Hemolysis was inhibited by sucrose, an osmotic protectant, suggesting that the initial action of HlyA on erythrocytes is to raise the basal cation permeability of the cell membrane. The most likely cytolytic mechanism is thus the formation of transmembrane lesions such as homopolymer pores in target cells, as has been found for toxins from numerous other bacterial pathogens.

Amino Acid Sequence↗
PubMed1975

Physiologic characteristics of vestibular first-order canal neurons in the cat. I. Response plane determination and resting discharge characteristics.

The response plane and resting rate characteristics of first-order, vestibular, semicircular canal neurons were studied in 67 cats under sodium pentobarbital anesthesia using single-unit recording techniques in the eighth nerve. Five hundred fifty-nine units were classified as to the canal they were associated with by employing an identification technique based on physiologic response patterns to brief, high-level (up to 250 degrees/S2) angular accelerations delivered in various head positions. All horizontal canal neurons had increased firing rates to ampullopetal and all vertical canal units to ampullofugal endolymph flow. The average observed roll and pitch null points for each canal were used to determine the average sensitivity vectors for the right horizontal, anterior, and posterior canals. These sensitivity vectors were at a variance of 4.6-10.2 degrees from those predicted by anatomical measurements (3). The mean resting discharge characteristics of 318 first-order neurons was 36.0 spikes/s (range 0.50-114 spikes/s). No significant difference was noted between horizontal and anterior canal neurons on horizontal and anterior canal neurons on the basis of resting rate. The resting rate of the posterior canal neuron population was significantly lower. The regularity of the resting discharge varied in all three canals and the average coefficient of variation was 0.238 for the population, with a range of 0.298-1.030. The population distribution of all resting-rate statistical parameters appeared to be unimodal, indicating that first-order canal neurons may not be broken into discrete populations on the basis of resting-rate characteristics. Of 47 adequately examined first-order canal neurons, 25 demonstrated a repeatable and predictable alteration in their resting discharge as their position to gravity was reoriented. This alteration was usually nonadapting and varied in magnitude according to the degree of tilt and original starting position. Of 25 canal gravity units, 4 had nearby units from the same canal which were unresponsive to gravity, suggesting the effect was due to a limited distortion of the crista or cupula rather than an overall displacement of the cupula.

Acceleration↗